Filter for the separation of solids and liquids from muds and specifically those from industrial processing

ABSTRACT

A filter for the separation of solids and liquids from muds, and specifically those from industrial processing, includes a container and a filtering bag housed in the container for reception of the muds. The filter further includes a deformable membrane housed in the container and defining therein a closed volume of variable size. A fluid pump is provided, communicating with the volume, to vary the size of the volume by pumping fluid into the volume, thereby squeezing the filtering bag in the container.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a filter for the separation of solidsand liquids from muds and specifically those from industrial processing.

Before continuing it is noted that in the present description and theclaims the term muds means generally fluids of varying chemicalcomposition and different physical properties which contain dispersedsolid particles.

2. Description of the Background Art

The use of filters in industrial plants in general is now verywidespread for reasons of environment protection, originating in theever stricter standards applied and for more rigourously economicreasons. In many cases, indeed, environmental standards prescribe anobligation to dispose of a considerable number of substances fromindustrial processes in especially assigned centres. These substancesare mostly present in fluids such as sewage and various type of muds andsuspensions from chemical processes but it is not rare to find liquidsused for cooling of machines. To limit the volume of fluid to be treatedand reduce the quantity of material to be hauled in the disposal centresit is important to provide adequate separation of the solid componentfrom the liquid in the fluid.

In addition, confirming the usefulness of the above mentioned filters,those industrial processes in whose waste fluids there are substanceswhich it is advantageous to recover due to their high economic valuemust be taken into consideration. Of course, even in these cases theeffectiveness of the solid and liquid separation operation is quiteimportant.

From Italian patent no. 1.184.501 a filtering container is known for theseparation of solids and liquids in which are provided two mutuallymoving overlying parts of which the first or upper defines a chamber forreception of a bag full of muds to be filtered while the second or loweris designed to penetrate through the base of the first substantially inthe manner of a piston. As a result of the movement of the lower partthe bag of mud is deformed and compressed so that the liquid containedtherein can flow out through the filtering fabric of which the bag ismade.

Another example of a mud filter substantially similar to the onedescribed above is known from another Italian patent no. 1.188.227. Alsoin this second example there is a chamber for housing a bag of muds tobe filtered and in which the volume is swept by a compressed air drivenpiston.

Basically, for both the above cases, operation of the filters calls forthe relative movement of two coupled parts in which the filter structureis divided. Even though the procedures according to which said movementtakes place are different, in one case gravity is used while in theother compressed air is used, the technical solutions proposed areunsatisfactory, especially as concerns the size and constructioncomplexity of the filters obtained.

Indeed, there being provided two mutually moving parts, the travel ofthe latter necessitates adequate mechanical means, especially runningguides, drive means and everything else, which make the filters verycumbersome and complicated, especially-considering their yield andefficiency. This shortcoming must indeed be considered in the light ofthe industrial end purpose of these filters, which must treat highquantities of fluid while ensuring steady production over timeassociated with continuous operational reliability. It should be notedalso that the parts making up the filter operate in contact with liquidsof varying chemical composition in which there are also dispersed solidparticles. Thus their mutual movements take place in particularly severeenvironmental conditions and may easily lead to failure.

SUMMARY OF THE INVENTION

The problem of the present invention is to provide a filter for theseparation of solids and liquids from muds, and in particular those fromindustrial processing, where the number of moving parts is substantiallyreduced.

A filter apparatus is known from EP-A-0311716, wherein a conduit ishelically wound about the outside of a filter media; the conduit isexpanded by air pressure to break solid cake build up on the filtermedia during filtration.

This problem is solved by a filter for the separation of solids andliquids from muds and specifically those from industrial processing,comprising:

a container,

a filtering bag housed in the container for reception of the muds,

a deformable membrane housed in the container and defining therein aclosed volume of variable size,

fluid pumping means communicating with the volume, to vary the size ofthe volume by pumping fluid into the volume, thereby squeezing thefiltering bag in the container,

characterized by further comprising:

a first inlet mouth in the filtering bag for feeding the mud into thefiltering bag

a plurality of holes formed in the side wall of the container so thatthe filtered liquid can flow out,

elastic means for ensuring elastic expansion of the bag against thevariable volume.

In the container, squeezing of the filtering bag is achieved byenlarging the size of the volume defined by the membrane. Apart from theobvious slipping of expanding and contracting parts, there is noreciprocal movement between the parts of the filter: the filter is thussimple and reliable. The filtering bag being provided with elastic meansfor ensuring elastic expansion of the bag against the variable volume,when a squeezing phase is completed, the bag comes back to its originalexpanded shape, making it easier to discharge the solid and to supplyother muds.

The container may have any suitable shape. Preferably, the containercomprises:

a substantially tubular side wall extending between a first end having afirst opening and a second end having a second opening closed by aplate,

a cavity defined inside the container, open to the first and secondopenings, and in the filtering bag:

the first inlet mouth is open to the first opening of the container,

a second discharge mouth is open to the second opening of the container.

This construction ensures a good strength and easy operations whenfeeding the muds (into the first inlet mouth through the first opening)and removing the solid (from the second discharge mouth through thesecond opening).

Pumping means may be any suitable device to feed a fluid under pressure,preferably a water pumping means.

Preferably, the filtering bag includes a filtering fabric and a drainagescreen coupled together. This double layer construction makes itpossible the outflow of liquid during squeezing even from those portionsof the bag where the outer side is laying against a surface.

Preferably, the filter comprises a tension netting, formed substantiallylike a cradle and designed to receive the membrane together with thefiltering bag, the latter being fastened to the tension netting. Thenetting may help in keeping the filtering bag in shape while resting andin guiding its deformation under squeezing.

Preferably, the elastic means comprises elastic bands surrounding thefiltering bag, each elastic band being slidingly engaged in loop pocketsformed on the outer side of the filtering bag. Such means are verysimple and effective; moreover, when a bag must be replaced by a newone, the bands can be removed and used again with the new bag.

Preferably, the filtering bag is arranged in the container with alongitudinal fold extending radially inward of the container oppositethe membrane, the membrane being capable of expanding in the fold in apredominantly radial direction in relation to the container. This foldmakes the external surface--i.e. the filtering surface--of the filteringbag larger, with equivalent volume.

The membrane which makes the variable size volume may have any shape. Ina preferred embodyment, the membrane includes a flexible U-bent tubeextending between a first closed end located at the first end of thecontainer and a second end communicating with pumping means. Such asimple membrane is capable of furnishing a good expansion of the volumeand can easily operate under high pressure.

When the filtering process must be performed under very high pressure,it may be preferable that the membrane includes a bundle of flexibleU-bent tubes, connected in parallel. In fact, such structure gives asmaller expansion ratio but can withstand much higher pressures.

Preferably, when the membrane is a U-bent tube, it comprises a rigidU-shaped pipe located inside the tube at the region where the tube isbent. The rigid pipe ensures fluid communication between the twoportions of the tube, even when the membrane is deflated, avoiding therisk that the membrane does not deflate completely due to a flatteningin the region of the bent at the initial stage of deflation.

Preferably, the filter comprises a stop device including a tape arrangedin a loop around the volume, connected through a spring to a switch foroperation of the pumping means. This arrangement is intended to stopautomatically the inflation of the membrane in case a predeterminedmaximum expansion is achieved.

In a further aspect, the invention relates to a filtering bag, made outof a filtering fabric, for use in a filter according to the invention.Although in principle any filtering bag can be used in a filteraccording to the invention, it is highly preferred that the bag becapable of expanding elastically, because this ensures better operationof the filter, as explained above.

So, according to a first embodiment of the invention, the filtering bagcomprises:

a first inlet mouth to be associated with a first opening of a containerof the filter,

engagement means to be associated with elastic means for ensuringelastic expansion of the bag in the container.

In this embodiment, elastic means are not a part of the bag itself, butare associated thereto.

Preferably, in the above case, the engagement means comprises looppockets formed on the filtering bag for sliding engagement of elasticbands. It has already been discussed that this arrangement is preferredbecause of the possibility of using always the same elastic bands, evenwhen changing the filtering bag.

Alternatively, the filtering bag may itself include the elastic means,and so it comprises:

a first inlet mouth to be associated with a first opening of a containerof the filter,

elastic means for ensuring elastic expansion of the filtering bag in thecontainer.

Preferably, in both embodiments, the loop pockets are formed on outerside of the filtering bag, so it is easier to remove and to insert theelastic bands.

If the filtering bag has a substantially cylindrical shape, as it isnormally preferred, the loop pockets are preferably disposed alongcircular paths. This means that deformations of the filtering bag occursubstantially in a radial direction.

The filtering bag may be a disposable one, in the sense that it is to bedisposed once it is full of solid. This may be useful in some specialapplications. In general, it is preferred that the bag comprises asecond discharge mouth to be associated with a second opening of thecontainer. Once full of solid, the bag can be emptied by discharging thesolid through the discharge opening.

The filtering bag may or may not be provided with means for holding itin position inside the container. In general, the higher is the workingpressure, the more is advisable to provide holding means for the bag, toavoid incorrect displacements.

So, preferably the filtering bag comprises a longitudinal pocket, forengagement of a rod to be inserted in a longitudinal guide of thecontainer to hold the filtering bag in the container. This way ofholding the bag is particularly simple and at the same time particularlystrong and effective, since holding occur along the whole length of thebag.

Additional characteristics and advantages of the filter in accordancewith the present invention are set forth in the description of anexample of embodiment thereof given below by way of nonlimiting examplewith reference to the annexed drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partially sectioned perspective view of a filter inaccordance with the present invention;

FIGS. 2 to 4 show a cross section of the filter of FIG. 1 in respectiveoperating conditions;

FIG. 5 shows a longitudinal cross section of the filter of FIG. 1;

FIG. 6 shows a partially sectioned perspective view of a filtering bagfor use in the filter of FIG. 1;

FIG. 7 shows a partially sectioned perspective view of a differentembodiment of a filtering bag for use in the filter of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the Figs. and in particular to FIG. 1 reference number1 indicates as a whole a filter in accordance with the present inventionarranged above a tank 2 for collection of filtered liquids.

The filter 1 comprises a container 5 extending between a tapered firstend 5a provided with a first opening 6a and a second end 5b opposite thefirst one, provided with a second opening 6b, closed by a removable endplate 7. Plate 7 is fixed in a conventionally removable manner to thecontainer 5. The container 5 has a tubular side wall 5c extendingbetween the first and second ends 5a and 5b and provided with smallholes 8 designed to allow outward passage of the liquid separated by thefilter to run into the collection tank 2. The side wall, which in thisexample consists of a pierced metal sheet, could of course be providedin other forms such as for example a functionally equivalent metallicgrate.

In the container 5 is defined a cavity 9 communicating with the openings6a and 6b and with the holes 8, and in which is housed a filtering bag10.

Said filtering bag 10 extends longitudinally inside the cavity 9 of thecontainer 5 from a first inlet mouth 12a in correspondence of the firstend 5a to a second discharge mouth 12b in correspondence of the secondend 5b. The first mouth 12a is fixed to the first opening 6a by means ofa collar 10a, while the second mouth 12b is fixed to the second opening6b, by means of an elastically deformable ring 10b radially forcing thebag 10 against the side wall 5c of the container 5.

The bag 10 is provided with elastic means for ensuring elastic expansionof the bag 10 in the container 5. Such means include a number of elasticbands 14, surrounding the bag 10 and secured thereto by means of looppockets 14a formed on the outer surface of the bag 10. In addition, inthe embodiment of FIGS. 1 to 6, the bag 10 is kept folded longitudinallyto form a radially extending fold 13 in its lower part by means of thesame bands 14. In the embodiment of FIG. 7, instead, no fold isprovided.

The fold 13 is obtained by making the bag 10 with a cross section (seeFIG. 2) having a related perimeter sufficiently long to originate anexcess of fabric which can, precisely, be folded radially in relation tothe filtering bag 10 to form the above mentioned fold 13.

The filtering bag 10 is made with a two layers structure, including aninner layer 12 of filtering fabric and an outer drainage screen 15coupled together. The screen 15, known independently, is flexible andallows down flow of the liquid emerging therefrom during operation ofthe filter as explained below.

The filtering bag 10 is affixed at a plurality of points 20 to a tensionnetting 22 which has a cross section corresponding to an arc of thecircumference and constitutes a cradle for reception of the bag 10.Between the tension netting 22 and the bag 10 and in a position adjacentto the fold 13 is an elastic membrane 25 which is deformable in the fold13. The membrane 25 consists in this example of a flexible tubesubstantially bent in the form of a letter U and closed at its first end25a which is fixed by bolts 26 to the container 5 at the opening 6thereof. The flexible tube also communicates at another end 25b withpumping means 30 for supply of water to its interior. In practice, themembrane 25 defines inside the container 5 a closed volume V of variablesize.

In the filter 1, inside the container 5, are also provided dilatableelements 35 designed to detach the solid component of the filtered mudsfrom the filtering fabric 12. The dilatable elements 35 are housed inrespective seats 36 arranged peripherally in relation to the filteringbag 10 and, in particular, two of them are formed between two of thepoints 20 of attachment of the filtering bag 10 to the tension netting22 advantageously located near each other. Above the filtering bag 10there is another of the seats 36 formed by two points 37 for fasteningthe filtering fabric 12 to the drainage screen 15.

In addition, the latter seat 36, which is above the filtering bag 10, isjuxtaposed to a guide 38 made up of a pair of L sections 38a affixed tothe container 5 and designed to receive a rod 39 inserted in alongitudinal pocket 39a formed in the bag 10, to hold the filtering bag10 in the container 5.

The dilatable elements 35 have tubular form, closed at a first end andcommunicating at a second end 35a with an air compressor not shown inthe drawings. The ends 35a are located near the end 5a of the container5.

In the filter in accordance with the present invention there areprovided means 40 of feeding the muds into the bag 10 through the mouth12a thereof. The means are conventional and include conveyance ducts aswell as feed pumps only shown diagramatically in the drawings annexed tothe present description.

It is also noted that opposite the mud feed means 40 there is provided acheck valve 42 to prevent the muds to be filtered from flowing backthrough the mouth 12a of the bag 10 during operation of the filter.

Finally, to control operation of the filter 1 there are also providedconventional means designed to measure the pressure of the muds insidethe bag 10 and not shown while there is illustrated in detail a stopdevice 44 associated with the membrane 25. The device 44 consistsessentially of a tape 45 closed in a loop around the two branches bentin a U of the flexible tube which forms the membrane 25 and coupled witha spring 46 in turn connected with a switch 47 for control of thepumping means 30.

In addition, inside the flexible tube which constitutes the membrane 25there is a pipe 48, also flexible although stiffer than the membrane 25,located at the region where the tube is bent, right in the knee formedin the bent tube.

Additionally, a pair of guide membranes 49 may be provided on eithersides of the membrane 25. These membranes 49, inflated simultaneouslywith the membrane 25, do not cooperate in squeezing the bag 10 but onlyguide the expansion of the volume V toward the middle of the container5.

The functions of the elements of the filter 1 described above areclarified by the following description of the operation of the filter inaccordance with the present invention.

Since the capacity of the filter 1 and the bag 10 with which it isprovided are of course limited there are given below the operatingprocedures with which the filter 1 operates in relation to acorrespondingly limited Mount of muds present in the bag 10. Of coursethe following description can be applied to a continuous operation ofthe filter 1 merely repeating the successive phases in which itsoperation is articulated for the limited amount mentioned above.

Once the bag 10 is filled with muds by the feeding means 40, the checkvalve 42 is closed so that, as mentioned above, it prevents the mudsfrom flowing back. After the end of this preliminary phase, thefiltering bag 10 assumes the operational configuration shown in FIG. 2.

Starting from this operating condition, the membrane 25 is then deformedby feeding water into it with the pumping means 30 connected to its openend 25b. This causes a consequent increase in the volume V defined bythe membrane which is arranged as clearly illustrated in FIG. 3, i.e.the flexible tube bent and initially flattened deforms while expandingradially in relation to the filtering bag 10 inside the fold 13. Thedeformation of the membrane 25 causes a dual action on the bag 10containing the muds.

A first action is bag compression or squeezing, causing outward flow ofthe liquid present in the muds through the filtering fabric of the bag.Said outward flow is also aided by the presence of the drainage screen15 whose meshes constitute a hollow space into which the outward flowingliquid can run also at those points of the bag such as for example thoseat which the membrane 25 operates and in which the outward flow would beprevented because of a direct contact between the filtering fabric and acontinuous surface compressing it. Indeed, it is clear that if therewere a direct contact between the filtering fabric and the membrane orbetween the former and the wall of the container 5 where of course thereare no holes 8 thereof, the liquid in the muds could not pass out of thebag at these points.

The membrane 25 then causes a second action, i.e. deformation of the bag10 with the muds in it and which assumes a particular archedconfiguration thanks to which it is possible to obtain a nearly uniformthickness of the mass of muds measured radially in relation to thefiltering bag. Indeed, it is known that the uniform thickness is afactor aiding filtering efficiency.

It is noted that in the present embodiment the above actions produced bythe membrane 25 are achieved also as a result of the reaction forceoffered by the fixing points 20 of the bag 10.

Concerning the second action of the membrane 25, i.e. deformation of thebag 10 with the muds contained therein achieving a substantiallyconstant radial thickness, there should be noted the importance of thepresence of the fold 13. This constitutes a preferred location in whichthe membrane 25 can expand radially in relation to the filtering bag 10.

It is also noted that another effect of the presence of the fold 13 canbe readily inferred by comparing the configurations assumed by the bag10 in FIGS. 2 and 3. It is observed that the fold 13 permits practicallyincrease of the surface of the bag through which the liquid separatedfrom the muds is made to flow outward. This is understandable if it isremembered that if the bag 10 did not have this fold, its surfaceavailable for outward flow of the liquid separated from the muds wouldbe equal to that seen in FIG. 2 excepting the surface corresponding tothe presence of the fold 13. The effectiveness of the filter inaccordance with the first embodiment of present invention (FIGS. 1 to 6)for a given initial filling capacity is therefore greater than that of afilter according to the second embodiment (FIG. 7), i.e. not having afold. The embodiment without fold is preferrable for its simplerconstruction when a less efficient filtering action is anywayacceptable.

After complete compression of the bag 10 and related muds containedtherein, the membrane 25 is returned to a non-operating conditionallowing the water previously pumped into it to flow out. Elastic actionof bands 14 tends to expand the bag 10 to its original condition,thereby causing a compression of the volume V. It is also underscoredthat in the membrane 25 formed by a bent flexible tube such as in thecase considered, the pipe 48 is particularly advantageous. Indeed, itallows outflow of the water in the flexible tube even at its knee bend.Indeed, if the pipe were not provided, the weight of the muds and thepressure of the water remaining in the flexible tube would prevent downflow of the water in the branch of the tube extending from the closedend 25a.

At this point it is important to observe that the choice of a membranemade up of a flexible tube bent like the letter U allows theconsiderable advantage of achieving a deformation of the membrane,radially in relation to the filtering bag 10, without at the same timeexcessive expansion-thereof in width. In other words, it would have beenpossible to conceive having recourse to a straight flexible tube insteadof one bent into the shape of the letter U but in this case to securethe same radial deformation the tube to be used would have to have adiameter double that of the one used in the illustrated example so thatits deformation would have resulted in excessive space occupied and lessefficiency of penetration of the membrane 25 into the fold 13 of thebag.

In addition it should be noted that end plate 7 allows easy removal ofthe bag 10 and considerable facilitation of all filter maintenanceoperations in general.

Finally, for control of the operation of the filter there is to be notedthe presence of the stop device 44 which allows effective control of thedilatation of the membrane 25 and, consequently, also its action on thebag 10 with the muds. This device proved to be quite simple and reliablein operation because as the flexible tube which constitutes the membrane25 increases in size because of the amount of water pumped into it bythe means 30, the tape 45 of the device is placed under traction andwith it also the spring 46. At the maximum dilatation of the membrane 25the spring 46 disconnects the switch 47 which controls the pumping means30 thus preventing damage to the membrane.

With reference to FIG. 4 there is indicated the operation of thedilatable elements 35 provided in the filtering bag 10. Indeed, aftercompletion of the filtering operation just described, i.e. once themembrane 25 has returned to the non-operating condition, the dilatableelements 35 are in turn dilated by feeding into their interior airsupplied by the compressor provided for the filter. Said dilatationcauses detachment of the solid particles of the muds separated from thefiltering fabric of which the bag 10 is made to unclog it and make itready for another filtering phase.

This peculiarity of the filter in accordance with the present inventionis extremely advantageous for those muds in which the solid component isthe colloidal type or, in any case, adheres to the filtering fabric 12.

Naturally to the above embodiment of the present invention there can bemade modifications and variations depending on the different operatingcircumstances which might occur in practice.

One of these modifications could be that represented by a filter inwhich the bag 10 is not provided with the second mouth. In such a casethe bag is to be disposed together with the solid materials collectedtherein.

Another conceivable variation in comparison with the above descriptionscould consist of a filter in which the filter 1 does not include thetension netting 22. In this case it might be thought to arrange themembrane 25 and the bag 10 directly inside the container 5 whilefastening it thereto in a manner similar to the instruction given forthe above example.

It is clear that in the membrane 25 there could be delivered, instead ofthe water fed by the pumping means 30, air or another fluid achieving inany case the same deformation effect on the bent flexible tube. Asconcerns the latter, it is hardly necessary to point out that it couldbe replaced by other forms of membrane which should in any case displaythe same functional dynamics set forth above for the bent flexible tube.

In other words, membranes equivalent to the bent tube would be thosecapable of defining a variable volume V inside the filter container 5and communicating with the pumping means 30 so as to be able to deformthe membrane with water or some other fluid and consequently causingcompression of the muds present in the container and the desiredseparation of liquids and solids.

It should also be remembered that in the filters in accordance with thepresent invention the muds have been advantageously collected in the bag10 so that the action of the membrane 25 is aided by this fact inaccordance with the above description. Despite this, to achieve a filterin accordance with the instructions in conformity with the presentinvention a single filtering container in which to house the muds wouldsuffice together with the membrane defining in the container a volume ofvariable size.

Finally, it is noted that for the purpose of aiding the introduction ofmuds and avoiding seagnation thereof, in the filter example described-above the end 5a of the container 5 is tapered. This shape prevents thepresence of muds to be filtered in a zone of the filtering bag 10 where,if it were not provided, there would be felt edge effects and the actionof the membrane 25 would not be optimal.

I claim:
 1. Filter for the separation of solids and liquids from mudscomprising:a container (5), a filtering bag (10) housed in the container(5) for reception of the muds, a deformable membrane (25) housed in thecontainer (5) and defining therein a closed volume (V) of variable size,fluid pumping means (30) communicating with the volume (V), to vary thesize of the volume (V) by pumping fluid into the volume (V), therebysqueezing the filtering bag (10) in the container (5), a first inletmouth (12a) in the filtering bag (10) for feeding the mud into thefiltering bag (10), a plurality of holes (8) formed in the side wall(5c) of the container (5) so that the filtered liquid can flow out,elastic means (14, 14a) for ensuring elastic expansion of the bag (10)against the variable volume (V).
 2. Filter according to claim 1, whereinthe container (5) comprises:a substantially tubular side wall (5c)extending between a first end (5a) having a first opening (6a) and asecond end (5b) having a second opening (6b) closed by a plate (7), acavity (9) defined inside the container (5), open to the first andsecond openings (6a, 6b), and wherein in the filtering bag (10): thefirst inlet mouth (12a) is open to the first opening (6a) of thecontainer (5), a second discharge mouth (12b) is open to the secondopening (6b) of the container (5).
 3. Filter according to claim 1,wherein the pumping means includes water pumping means.
 4. Filteraccording to claim 1, wherein the filtering bag (10) includes afiltering fabric (12) and a drainage screen (15) coupled together. 5.Filter according to claim 1, comprising a tension netting (22), formedsubstantially like a cradle and designed to receive the membrane (25)together with the filtering bag (10), the latter being fastened to thetension netting (22).
 6. Filter according to claim 1, wherein theelastic means comprises elastic bands (14) surrounding the filtering bag(10), each elastic band (14) being slidingly engaged in loop pockets(14a) formed on the outer side of the filtering bag (10).
 7. Filteraccording to claim 2, wherein the filtering bag (10) is arranged in thecontainer (5) with a longitudinal fold (13) extending radially inward ofthe container (5) opposite the membrane (25), the membrane (25) beingcapable of expanding in the fold (13) in a predominantly radialdirection in relation to the container (5).
 8. Filter according to claim2, wherein the membrane (25) includes a flexible U-bent tube extendingbetween a first closed end (25a) located at the first end (5a) of thecontainer (5) and a second end (25b) communicating with pumping means(30).
 9. Filter according to claim 8, wherein the membrane (25) includesa bundle of flexible U-bent tubes, connected in parallel.
 10. Filteraccording to claim 8, wherein the membrane (25) comprises a pipe (48)located inside the tube at the region where the tube is bent.
 11. Filteraccording to claim 1, comprising a stop device (44) including a tape(45) arranged in a loop around the volume (V), connected through aspring (46) to a switch (47) for operation of the pumping means (30).12. Filter according to claim 1, with said filtering bag comprising:afirst inlet mouth (12a) to be associated with a first opening (6a) of acontainer (5) of the filter (1), engagement means (14a) to be associatedwith elastic means (14) for ensuring elastic expansion of the bag (10)in the container (5).
 13. Filter according to claim 12, wherein theengagement means comprises loop pockets (14a) formed on the filteringbag (10) for sliding engagement of elastic bands (14).
 14. Filteraccording to claim 1, comprising:a first inlet mouth (12a) to beassociated with a first opening (6a) of a container (5) of the filter(1), elastic means (14, 14a) for ensuring elastic expansion of thefiltering bag (10) in the container (5).
 15. Filter according to claim12, wherein the elastic means comprises:elastic bands (14) to beassociated with the filtering bag (10), loop pockets (14a) formed on thefiltering bag (10) for sliding engagement of the elastic bands (14). 16.Filter according to claim 13, wherein the loop pockets (14a) are formedon outer side of the filtering bag (10).
 17. Filter according to claim13, having a substantially cylindrical shape, wherein the loop pockets(14a) are disposed along circular paths.
 18. Filter according to claim12, comprising a filtering fabric (12) and a drainage screen (15)coupled together.
 19. Filter according to claim 12, comprising a seconddischarge mouth (12b) to be associated with a second opening (6b) of thecontainer (5).
 20. Filter according to claim 12, comprising alongitudinal pocket (39a), for engagement of a rod (39) to be insertedin a longitudinal guide (38) of the container (5) to hold the filteringbag (10) in the container (5).
 21. Filter according to claim 15, whereinthe loop pockets are formed on the outer side of the filtering bag. 22.Filter according to claim 15, having a substantially cylindrical shape,wherein the loop pockets are disposed along circular paths.
 23. Filteraccording to claim 14, comprising a filter fabric and a drainage screencoupled together.
 24. Filter according to claim 14, comprising a seconddischarge mouth to be associated with a second opening of the container.25. Filter according to claim 14, comprising a longitudinal pocket, forengagement of a rod to be inserted in a longitudinal guide of thecontainer to hold the filtering bag in the container.